1. Field of the Invention
The present invention relates to a method for controlling a single lens reflex camera having a preview function (to confirm the depth of field) and a single lens reflex camera.
2. Description of the Related Art
In a known preview apparatus having a preview switch which can be actuated independently of the release switch, an electrically driven motor is rotated in the forward direction, so that the preview operation and the release operation are effected sequentially during a single revolution of the single-revolution cam gears which are rotated in association with the motor (e.g., Japanese Unexamined Patent Publication No. 2-77045 or U.S. Pat. No. 5,257,052 corresponding thereto). In this preview apparatus, when the motor is rotated in the forward direction, the stop-down operation to close the aperture is first effected by the cam gears and thereafter, the upward movement of the mirror and the movement of the shutter are carried out upon completion of the stop-down operation.
With this structure, if the release switch is turned ON during the preview operation, the photographing operation begins. Consequently, the exposure is controlled in accordance with old or previous photometering data obtained when the preview switch has been turned ON or after the stop-down operation to reduce the aperture size has been effected. In particular, in a full-open (open aperture) photometering camera, no precise photometering data can be obtained. It is in theory possible to return the cam gears to the respective initial positions by reversing the motor from the preview position, so that the full-open photometering operation can be carried out. However, since it is necessary to reciprocally move the cam gears between the preview position and the initial positions prior to the release operation, the time lag between the release operation and the movement of the shutter is undesirably increased.
It is an object of the present invention to provide a control method of a single lens reflex camera having a preview function and a single lens reflex camera having a preview function in which the exposure can be precisely controlled if the release switch is depressed during the preview operation.